CO2升高和阳光紫外辐射对坛紫菜生长和光合特性的耦合效应

大气CO₂持续升高,导致溶入海水中的CO₂增多,海水表层的H+浓度增加,从而引起海洋酸化。为了探讨近岸定生大型海藻对这种环境变化的响应,本文选择经济海藻坛紫菜为实验材料,研究海洋酸化与紫外辐射对藻体生长以及光合特性的影响。实验分两个CO₂处理,分别为正常空气水平(390 ppmv)和高CO₂水平(800 ppmv); 三种辐射处理,分别为全波长辐射(PAB)、滤除紫外线B(PA)和仅接受可见光处理(PAR)。研究结果表明,CO₂培养下的坛紫菜,在仅有可见光(P)或者同时有紫外线A(PA)存在的情况下,显著促进藻体的生长;但在全波长辐射处理下(PAB),这种作用不明显。高CO₂降低了藻体在P和PA处理下的光合作用速率,但对PAB处理作用不显著。高CO₂处理下的藻体,UV-B显著降低了全波长辐射下藻体紫外吸收物质的含量,但在正常CO₂水平下,紫外辐射的作用不显著。这表明高CO₂导致的生长优势被紫外辐射的负面效应所抵消,在全球变化的过程中,紫外辐射的进一步加强在海洋酸化的背景下甚至有可能降低坛紫菜的产量。

Co-effects of CO2 and solar UVR on the growth and photosynthetic performance of the economic red macroalga Porphyra haitanensis

Increasing CO₂ in the atmosphere makes the oceans take up more CO₂ from the air, and H⁺ concentration in surface seawater increase, which was known as ocean acidification. In order to find the responses of macroalgae to the environment changes, The economic macroalga Porphyra haitanensis was selected to study the co-effects of solar UVR and CO₂ on the physiological performances of the thalli. The experiments set up two CO₂ levels, 390ppmv and 800ppmv, and three solar light treatments, full spectrum solar radiation (PAB), UV-B was cutting off and PAR only. Our results showed that the enhance of the growth of Porphyra haitanensis was found in the thalli cultured under high CO₂ condition compared with that under ambient CO₂ condition when the UV-B or UVR were cut off, but no significant difference was found in the thalli receiving full solar radiation. UV-B decreased the contents of UV-screening compounds in Porphyra haitanensis grown under elevated CO₂, while UV has no apparent effect on it when the thalli cultured at ambient CO₂ levels. It showed that the advantage of CO₂ in growth of Porphyra haitanensis was offseted by the full spectrum solar radiation, and the production of the economic macroalga might decrease in future ocean where solar UV radiation will futher increase.